LIBRARY

SYNOPSIS

DESCRIPTION

The sched_setscheduler() system call sets the scheduling policy and
scheduling parameters of the process specified by pid to policy and the
parameters specified in the sched_param structure pointed to by param,
respectively. The value of the sched_priority member in the param
structure must be any integer within the inclusive priority range for the
scheduling policy specified by policy.
In this implementation, if the value of pid is negative the system call
will fail.
If a process specified by pid exists and if the calling process has
permission, the scheduling policy and scheduling parameters will be set
for the process whose process ID is equal to pid.
If pid is zero, the scheduling policy and scheduling parameters are set
for the calling process.
In this implementation, the policy of when a process can affect the
scheduling parameters of another process is specified in IEEE Std
1003.1b-1993 (“POSIX.1”) as a write-style operation.
The scheduling policies are in <sched.h>:
[SCHED_FIFO] First-in-first-out fixed priority scheduling with no round
robin scheduling;
[SCHED_OTHER] The standard time sharing scheduler;
[SCHED_RR] Round-robin scheduling across same priority processes.
The sched_param structure is defined in <sched.h>:
struct sched_param {
int sched_priority; /* scheduling priority */
};
The sched_getscheduler() system call returns the scheduling policy of the
process specified by pid.
If a process specified by pid exists and if the calling process has
permission, the scheduling parameters for the process whose process ID is
equal to pid are returned.
In this implementation, the policy of when a process can obtain the
scheduling parameters of another process are detailed in IEEE Std
1003.1b-1993 (“POSIX.1”) as a read-style operation.
If pid is zero, the scheduling parameters for the calling process will be
returned. In this implementation, the sched_getscheduler system call
will fail if pid is negative.

RETURNVALUES

Upon successful completion, the value 0 is returned; otherwise the
value -1 is returned and the global variable errno is set to indicate the
error.

ERRORS

On failure errno will be set to the corresponding value:
[ENOSYS] The system is not configured to support this
functionality.
[EPERM] The requesting process doesn not have permission as
detailed in IEEE Std 1003.1b-1993 (“POSIX.1”).
[ESRCH] No process can be found corresponding to that
specified by pid.
[EINVAL] The value of the policy argument is invalid, or one or
more of the parameters contained in param is outside
the valid range for the specified scheduling policy.